Information recording medium with expanded information recording capability

ABSTRACT

An optical disk comprising a substrate  4 , and a plurality of tracks  269  to  273  formed on the substrate  4 , wherein the plurality of tracks  269  to  273  include groove tracks  270, 272  consisting of a plurality of grooves mutually space apart by a fixed space, and land tracks  269, 271, 273  consisting of areas between the groove tracks, wherein the borders  14, 15  between the groove tracks and the land tracks represent information using the waveforms from their wobbling patterns, wherein the period of the wobbling waveforms of the borders  14, 15  are constant on each border, but the wobbling waveforms of the opposite portions of the borders across the track are shifted in phase by a predetermined phase difference.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional of U.S. application Ser. No. 08/955,368, filed Oct.21, 1997, now U.S. Pat. No. 6,069,870, the subject matter of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information recording medium foroptically recording or reproducing information, and an informationrecording and reproducing apparatus for recording or reproducinginformation on the information recording medium.

2. Prior Art

Optical disks are known, such as compact disks and magnetooptical disks,which optically record information by changes in the reflectance factoror changes in the polarization direction of reflected light, forexample. A track 261 is formed in a spiral form on the surface of anoptical disk as shown in FIG. 26. Along this track on the optical disk,information marks caused by the changes in the reflectance factor or thechanges in the polarization direction of the reflected light are formedto record information on a surface of an optical disk 260.

A circuit of the track 261 is divided into an integral number of blocks262. Each block 262 is divided according to a predetermined disk formatinto a plurality of areas, on each of which user data and controlinformation for use in recording or reproducing user data is recorded.The blocks are also called sectors.

As an example of disk formats, the format of a rewritable magnetoopticaldisk 130 mm in diameter and with a recording capacity of 1.3 GB,standardized by ISO (international Standardization Organization) will bedescribed with reference to FIG. 25. In FIG. 25, the numbers given belowthe information areas denote the numbers of bytes of the related itemsof information.

The capacity for one block (sector) 262 is 1410 bytes. One blockincludes at its leading end a preformatted header segment 250 of 63bytes. In the format of FIG. 25, information in the preformatted header250 is recorded with information marks consisting of prepits formed atthe time of manufacture of the optical disk. Information other than thatin the preformatted header segment 250 is not preformatted, but isrecorded with rewritable information marks.

The preformatted header segment 250 includes a sector mark segment (SM)256 to record information to indicate the leading end of this block, aVFO segment 257, an address mark segment (AM) 258, an addressinformation segment (ID) 259, and a PA segment 267. The addressinformation segment (ID) 259 has recorded therein information toindicate the location of this block 262 on the optical disk 260, and hasa self-clocking function to generate a clock signal from its owninformation during reproduction. The VFO segment 257 has recordedtherein information to designate a specific frequency for pull-in whengenerating a clock signal for the address information segment 259. TheAM segment 258 has recorded therein information to indicate that thereis an address information segment (ID) 259 in the subsequent segment. Ineach preformatted header, a VFO segment 257, an AM segment 258, and anaddress information segment 259 are arranged twice in succession, andthe PA segment 267 is provided to adjust the length of the informationmarks in the whole area of the preformatted header segment 250.

Behind the preformatted header segment 250, an ALPC-GAPS segment 251 isprovided. The ALPC-GAPS segment 251 includes a FLAG segment 265 to showwhether or not data has been recorded in a data field 254, an ALPCsegment 266 for recording information to control the power of the laserin recording, and GAP segments 264 as buffer portions placed between thesegments.

Following this, a data field 254 for recording user data is provided.The data field 254 also has a self-clocking function. Before the datafield 254, a VFO segment 252 and a SYNC segment 253 are provided. In theVFO segment 252, a specific frequency is recorded for pull-in forgenerating a clock signal in synchronism with data when reproducing datafrom the data field 254. In the SYNC segment 253, information abouttiming for demodulating information during reproduction is recorded.

In the data field 254, RESYNC segments 268 and data segments 267 arealternately provided. The RESYNC segments 268 are provided to re-attainsynchronism when loss of synchronism occurs between data and clockduring the self-clocking operation. Data 267 consists of information1040 bytes long, which includes user data of 1024 bytes, a CRC segmentto check if user data is read correctly, and a DMP segment to show whereerror data is when error data occurs due to corruption of data, and ECCcodes of 160 bytes added to correct the error data. When recording, twobytes of RESYNC 268 are added for every 30 bytes of data 267.

In the rear of the data field 254, a buffer segment 255 is provided. Theclock for recording information has a fixed frequency, and thereforewhen a variation occurs in the rotating speed of the motor to drive theoptical disk or when the center of the track 261 deviates from thecenter of rotation, the linear velocity of the laser beam for writing onthe track 261 varies, but the buffer 255 absorbs this variation.

In the conventional format standardized by ISO, in one block 262 of 1410bytes, the user data capacity at which the user can record data is 1024bytes in the data field 254. Therefore, the recording efficiency of userdata is 1024/1410, namely, 72.6%. The remaining 27.4% is accounted forby the address information segment 259 and control signals of VFOsegments 257, 252, when reproducing so that the recording efficiency ofuser data is not so high.

For this reason, to improve the recording efficiency of user data,JP-A-49-103515 discloses a technique by which the track is made tofluctuate with minute waves, and address information of the track isrecorded by the variation of the frequency of the waves. Specifically,the track is formed during the manufacture of the optical disk such thatthe center of the track is made to fluctuate minutely (by wobbling) inthe width direction of the track, the frequency of this wobbling isvaried along the longitudinal direction of the track, by which theaddress information of the track is represented. Since the addressinformation is recorded by the wobbling of the track, it is notnecessary to record the address information with the information marks,and accordingly the area for recording user data with the informationmarks can be increased. Thus, the recording efficiency of user data canbe enhanced.

However, the above technique in JP-A-49-103515 is unable to use a trackwidth smaller than the diameter of the beam spot of the laser beam inreproduction. The reason for this is that if the track width is narrowerthan the beam spot, the leakage of information from adjacent tracksincreases, making it difficult to reproduce information correctly.

In literature titled International Symposium on Optical Memory 1995 (ISO'95) TECHNICAL DIGEST Fr-D4 “A NEW DISC FOR LAND/GROOVE RECORDING ON ANMSR DISC, a land/groove track structure was proposed in which, as shownin FIG. 1, grooves 3 are formed mutually separated by a fixed space onthe surface of the optical disk, and while those grooves 3 are used astracks, lands 2 between the grooves 3 are also used as tracks. In thisstructure, since the tracks on the lands 2 are adjacent to the tracks inthe grooves 3, there is a level difference corresponding to the depth hbetween the adjacent tracks. Therefore, as shown in FIG. 1, the diameterof the reproducing beam spot 1 of the laser beam is larger than thetrack width in the reproduction process, and also when the reproducingbeam spot 1 extends over the adjacent tracks on both sides of the trackfrom which data is reproduced, with the phases of reflected beams fromthe adjacent tracks, a phase difference corresponds to the difference inthe height h of the tracks, thus making it possible to prevent theleakage of information from the adjacent tracks. Therefore, the trackwidth can be made smaller than the beam spot diameter, so that the trackdensity can be increased. Also in this literature, as shown in FIG. 1,another technique was revealed in which the border between the land 2and the groove 3 is made to wobble, and address information is recordedwith the wobbling frequency. Also, a structure was proposed in which thetrack width is smaller than the reproducing beam spot, and there arealways two borders between the land 2 and the groove 3 within thereproducing beam spot 1, and therefore address information isrepresented by wobbling only one of the two borders.

However, in the structure in that literature as shown in FIG. 1, sincethe part wobbles is the border between the land and the groove, thewobbling motion of the border is shared by the track on the land sideand the track on the groove side. Therefore, not only when the center ofthe reproducing beam spot 1 is located on the land side 2 but also whenthe beam spot is located on the groove side, the wobbling motion of thesame border is detected, and accordingly address information specifiedby the wobbling frequency is produced. Hence, it is impossible to decidefrom the address information reproduced by wobbling whether thereproducing beam spot 1 is on the track of the land side 2 or on thetrack of the groove side 3. If for some reason the tracking servo failsto keep track and the reproducing beam spot shifts to the adjacenttrack, this cannot be detected from address information, with the resultthat there is a possibility that information of the adjacent track isreproduced and recorded by mistake.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide an informationrecording medium which stores address information in such a manner thatinformation can be securely recorded or reproduced on the target track,while increasing the track density.

A second object of the present invention is to provide an informationreproducing apparatus for reading information from such an informationrecording medium in this patent application.

To accomplish the first object mentioned above, the present inventionprovides an information recording medium as shown below, that is:

an information recording medium comprising:

a substrate;

a plurality of tracks formed on said substrate, said plurality of tracksincluding a plurality of groove tracks consisting of a plurality ofgrooves formed mutually spaced apart by a fixed space, and a pluralityof land tracks formed in areas between adjacent groove tracks,

wherein said grooves are so formed as to represent information bywobbling waveforms of borders wobbling between said groove tracks andsaid land tracks, wherein the period of the wobbling waveforms of saidborders is fixed, and wherein the phases of the wobbling waveforms ofsaid borders are such that the waveforms of the opposing portions of theadjacent borders facing each other across each said track are out ofphase with each other by a predetermined phase difference.

To accomplish the second object mentioned above, the present inventionprovides an information reproducing apparatus as shown below, that is:

an information reproducing apparatus comprising:

a rotating portion to rotate an information recording medium on whichinformation has been recorded by wobbling said borders on both sides ofa track with different phases;

a beam irradiating portion for irradiating a beam spot on said track ofsaid information recording medium;

a photodetector for receiving a reflected beam of said beam spot fromsaid information recording medium;

detection means for detecting a composite waveform including waveformson said borders on both sides from the received beam intensity of saidphotodetector;

reference signal generating means for generating two reference signalsrespectively synchronized with the phases of the wobbling of saidborders on both sides; and

information reproducing means for separately reproducing information ofthe wobbling waveform of said borders on both sides by multiplying saidcomposite waveform by said two reference signals respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing the track structure of theland/groove method of the conventional optical disk;

FIG. 2 is an explanatory diagram showing the wobbling waveforms of theborders of tracks 270, etc. of the optical disk according to a firstembodiment of the present invention;

FIG. 3 is an explanatory diagram showing the wobbling waveforms of theborders of tracks 270, etc. of the optical disk according to the firstembodiment of the present invention;

FIG. 4 is an explanatory diagram showing the principle of reproducingaddress information from the wobbling waveforms of the borders of thetracks 270, etc. of the optical disk of the first embodiment of thepresent invention;

FIG. 5A is an explanatory diagram showing a part of the structure of therecording and reproducing apparatus for recording or reproducinginformation on the optical disk according to the first embodiment of thepresent invention;

FIG. 5B is a block diagram showing a detailed structure of a circuit 41in FIG. 5A;

FIG. 6 is an explanatory diagram showing the movement of the beam spoton an original disk of an optical disk according to a second embodimentof the present invention when exposing the original disk to light;

FIG. 7A is an explanatory diagram showing an example of the shape of thesync area 12 on the optical disk according to the first embodiment ofthe present invention;

FIG. 7B is an explanatory diagram showing an example of the shape of thesync area 12 on the optical disk according to the first embodiment ofthe present invention;

FIG. 7C is an explanatory diagram showing an example of the shape of thesync area 12 on the optical disk according to the first embodiment ofthe present invention;

FIG. 8 is a block diagram of a light exposure system for producing anoriginal disk for the optical disk according to the second embodiment ofthe present invention;

FIG. 9A is a block diagram showing a detailed structure of the addressrecording control circuit 73 of the exposure system of FIG. 8;

FIG. 9B is a block diagram showing a detailed structure of thedeflection signal generator 91 of FIG. 9A;

FIG. 10 is an explanatory diagram showing waveforms of signals used inthe circuits related to FIGS. 3 and 9;

FIG. 11A is a block diagram showing a circuit structure for reproducingaddress information on the optical disk according to a third embodimentof the present invention;

FIG. 11B is a block diagram showing a detailed structure of thesynchronous signal generator 41 in FIG. 11A;

FIG. 12 is a block diagram showing a more detailed circuit structure ofa part of the circuit of FIG. 11A;

FIG. 13 is an explanatory diagram showing waveforms of signals used inthe circuit of FIG. 15A;

FIG. 14A is an explanatory diagram showing a modulation rule used in themethod of recording or reproducing address information on the opticaldisk according to a fourth embodiment of the present invention;

FIG. 14B is an explanatory diagram for explaining bit combinations onthe track borders, used in the recording or reproducing method of FIG.14A;

FIG. 15A is a block diagram showing a circuit structure for reproducingaddress information on the optical disk in the recording or reproducingmethod of FIG. 14;

FIG. 15B is a block diagram showing a detailed structure of thesynchronous signal generator 41 of FIG. 15A;

FIG. 16 is a block diagram showing a more detailed structure of a partof the circuit of FIG. 15A;

FIG. 17A is an explanatory diagram showing a modulation rule used in themethod of recording or reproducing address information on the opticaldisk according to a fifth embodiment of the present invention;

FIG. 17B is an explanatory diagram showing examples of data each bit onthe track borders, modulated by the recording or reproducing method ofFIG. 17A;

FIG. 18A is an explanatory diagram showing an example in which timingdata 1800 is included in address information in the fifth embodimentshown in FIGS. 17A, 17B;

FIG. 18B is an explanatory diagram showing an example in which timingdata 1800 is included in address information in the fifth embodimentshown in FIGS. 17A, 17B;

FIG. 19 is an explanatory diagram showing an example of addressinformation recorded by the recording or reproducing method of FIGS.14A, 14B;

FIG. 20 is a block diagram showing a circuit structure for detecting atrack shift signal from a detection signal of address information on theoptical disk according to a sixth embodiment of the present invention;

FIG. 21 is an explanatory diagram showing waveforms of signals detectedby the circuit in FIG. 20;

FIG. 22 is an explanatory diagram for explaining a relationship betweenthe beam spot and the track shape on the original disk exposed by theexposure system in FIG. 9A, and showing on an enlarged scale the groovesformed on the information recording medium (disk) in the presentinvention;

FIG. 23 is an explanatory diagram showing the area scanned by the beamspot when reading one bit on the track 272 of the optical disk in FIG.3;

FIGS. 24A to 24H are explanatory diagrams showing waveforms of signalswhen demodulating address information using the circuit of FIG. 5A;

FIG. 25 is an explanatory diagram showing an example of ISO format ofthe conventional magnetooptical disk;

FIG. 26 is an explanatory diagram showing a relationship between thetracks and the blocks of the conventional optical disk;

FIG. 27 is an explanatory diagram showing the information mark andwobbling waveforms of the borders of tracks on the optical diskaccording to the first embodiment of the present invention;

FIG. 28 is an explanatory diagram showing the structure of the opticalsystem of the optical head 1292 of the optical disk recording andreproducing apparatus according to the first embodiment of the presentinvention; and

FIG. 29 is a block diagram showing the structure of the whole opticaldisk recording and reproducing apparatus according to the firstembodiment of the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

A first embodiment of the present invention will be described.

To begin with, an optical disk according to the first embodiment of thepresent invention will be described.

As shown in FIGS. 2 and 27, an optical disk 4 according to the firstembodiment is formed as an optical disk of the land/groove trackstructure which uses grooves 270, 272, etc. and lands 269, 271, 273,etc. as the tracks formed mutually spaced a fixed distance apart in aspiral form with respect to the center of the disk. As shown in FIG. 2,one circuit of the track 270, for example, is divided into an integralnumber of blocks 11, and each block 11 is divided into a synchronous(sync) area 12, a data area 16, and a CRC area 17. The blocks 11 may beprovided by a generally well-known method. For example, the CAV(Constant Angular Velocity) method may be used in which the number ofblocks 11 per circuit of the track is the same from the innermost trackto the outermost track of the optical disk 4, or the M-CAV (ModifiedCAV) method may be used in which the optical disk 4 is divided into somezones in the radial direction, and the same number of blocks 11 are ineach circuit of the tracks in the same zone, and the number of blocks 11per circuit of the track is greater for outer zones and smaller forinner zones.

Data in the data area 16, as shown in FIG. 27, is recorded withinformation marks formed along the track 270, etc. Address information13 on the tracks 270, etc. is recorded by wobbling the borders of thetracks 270, etc. of the data area 16. Therefore, data using informationmarks 274 and the address information 13 using wobbling of the border ofthe track are recorded simultaneously in the same area.

Meanwhile, the information marks 274 of the optical disk according tothe first embodiment are formed by heating the recording film 11 of theoptical disk 4 by condensing the laser beam on the surface of theoptical disk as described later, and the information mark differs inlight reflectance factor from that of the surrounding area. However, theoptical disk 4 according to the present invention is not limited to thetype in which the information marks 274 are formed as thermally formedtraces having a different reflectance factor from that of thesurrounding area. Optical disks may be used which apply other kinds ofinformation marks, such as a mark whose direction of polarizationdiffers from that of the surrounding area, or a mark formed by othermethods.

The sync area 12 is used to generate a reference signal and a clocksignal used when reading data in the address information 13 and the dataarea 16. The composition of the sync area will be described later. TheCRC area 17 has recorded therein information used to check whether userdata is read correctly. This information is the same as in the CRCsegment used in the conventional format in FIG. 25. Information in theCRC area 17 is recorded with the information marks 274. Note that in thefirst embodiment, also in the CRC area 17, like in the sync area 12,address information 13 is recorded by wobbling the borders 14, 15 of thetracks 270, etc.

In the first embodiment, address information 13 is recorded withdifferent wobbling waveforms, as shown in FIG. 27, which are generatedby wobbling the borders 14, 15 of the tracks 270, etc. of the data area16 and the CRC area 17 in different wobbling waveforms as shown in FIG.27. Address information 13 indicates where the borders 14,15 are locatedon the optical disk 4. Therefore, even if there is only one groove track270, the wobbling waveform differs between the border 14 at the innercircumference side and the border 15 at the outer circumference side ofthe groove track 270.

Specifically, as shown in FIG. 3, the borders 14, 15 of the tracks 270,etc. are partitioned, and each subdivision is denoted as one bit, anddata “0” or data “1” are represented by the wobbling waveforms.Meanwhile, the number of bits in each block is fixed regardless ofwhether the block is located at the track on the inner circumferenceside or at the track on the outer circumference side. The number ofperiods of the wobbling waveforms should be decided so that apredetermined number of waves are included in each bit area (fiveperiods in FIG. 3). The phase of the wobbling waveforms should bedecided so that in a given bit, the wobbling waveform of data “0” isidentical in oscillation period with the wobbling waveform of data “1”,but those waveforms are 180 degrees out of phase with each other (aphase difference of 180 degrees). However, the phase of the wobblingwaveform on the border 14 on the inner circumference side of the groovetrack 270 or 272 should invariably be set to lag or lead by on that ofthe wobbling waveform on the border 15 on the opposite, outercircumference side of the track, by 90 degrees, in other words, thosewaveforms should have an orthogonal relationship. As the phases are setas described above, even seen from the land track 271, the wobblingwaveform on the border is on the inner circumference side lags or leadson that of the wobbling waveform on the border 14 on the opposite, outercircumference side by 90 degrees in phase, in other words, thosewaveforms have an orthogonal relationship. Because the adjacent bitsrepresent different pieces of data because the items of the wobblingwaveforms are set for each bit, when the adjacent bits representdifferent data, that is, when the adjacent bits represent “1” “0” or “0”“1”, the wobbling waveform is discontinuous on the border over the twobits.

FIG. 3 shows the wobbling waveforms of the borders 14, 15 of the tracks270, etc. In FIG. 3, the tracks 270, 271, and 272 are drawn in straightlines for the sake of convenience, and they are concentric on an actualoptical disk 4. As shown in FIG. 3, on the groove track 270, data “011”is represented on the border 14 on the inner circumference side, anddata “101” is represented on the border 15 on the outer circumferenceside by wobbling waveforms. Data “110” is represented by wobbling of theborder on the inner circumference side of the groove track 272, whiledata “111” is represented on the outer circumference side.

As has been described, by recording different items of addressinformation 13 on the track, which indicate the respective locations ofthe borders 14, 15 on the optical disk 4, it is therefore possible toread address information 13 of the borders 14, 15 on both sides of thetrack when reproducing the information marks 274. For example, by movingthe reproducing beam spot 1 along the groove track 270 to readinformation on the groove track 270, it is possible to read addressinformation “011” from the border 14 on the inner circumference side and“101” from the border 15 on the outer circumference side simultaneouslywith data by the information marks 274. By a combination of “011” and“101”, it can be confirmed that the track irradiated by the reproducingbeam spot 1 is the groove track 270. If the tracking servo should failto keep track and it becomes obscure which track the reproducing beamspot 1 is irradiating, but so long as address information 13 which isdetected is a combination of “101” and “110”, it can be known that thereproducing beam spot 1 is shifted to the land track side 271. Thus, itis easy to decide which the beam spot 1 is irradiating, the groovetrack, such as 270 or the land track, such as 271.

Meanwhile, the wobbling waveforms are formed by forming grooves, 270,272, and so on, such that the borders of the grooves assume wobblingwaveforms. This will be described later. Though FIG. 3 shows that thereare waveforms of five periods in one bit, the number of periods is notlimited to five, but may be any number.

For an actual structure of the sync area 12, any of the structures ofFIGS. 7A, 7B and 7C may be used. FIG. 7A shows a structure havingoptically identifiable marks 51, 52, 53 and 54. In this case, in thesync area 12, grooves, such as tracks 270, 272, are not formed in thesync area 12, and the sync area 12 is flush with the surface of landtracks, such as 271. The marks, such as 51, are pits formed on thesurface, and are formed simultaneously in the process of forming groovesfor groove tracks 270, 272 during the manufacture of the optical disk 4.Those marks 51, 52, 53 and 54 are arranged close to the borders 14, 15of the tracks, 270 etc., and are shared by the adjacent tracks. Forexample, the sync area 12 of the groove track 270 has the marks 52, 53,while the sync area 12 of the groove track 272 has the marks 53, 54. Thespace in the track-lengthwise direction of two marks, such as 51, 52etc. in the sync area 12 is formed so as to be synchronous with thewobbling waveforms of the address signal. Therefore, by dividing thefrequency of a signal obtained from the space between the marks, such as51, of the sync area 12, a reference signal synchronous with thewobbling waveform can be generated. In addition, two marks, such as 51,52 are arranged not in the center of the track 270 etc. but in thevicinity of the border 14, 15 so that those marks wobble to the left andright with respect to the center of the track 270 etc. Therefore, byusing a well-known sampling-servo method in order to find a leveldifference between the marks 51 and 52, a shift of the reproducing beamspot 1 from the track center can be known. Thus, according to a signalfrom the sync area 12, it is possible to correct the shift of addressinformation 13 from the track.

The sync areas 12 of structures in FIGS. 7B and C have groove tracks270, 272 formed therein to represent sync signals by the wobblingwaveforms at the borders 14, 15 of the tracks, such as 270. In the syncarea 12 in FIG. 7B, the border 14 on the inner circumference side andthe border 15 on the outer circumference side of the groove track 270etc. have wobbling waveforms of the same period and phase. The wobblingwaveforms in the sync area 12 are made to have a larger amplitude thanthat of address information 13 so that the wobbling waveforms in thesync area 12 can be detected easily. In this structure, regardless ofwhere the reproducing beam spot 1 is irradiating, the groove tracks 270,272, or the land track 271, or the intermediate regions, the sync area12 can be detected by detecting a region having the wobbling waveformsof the sync area. In the structure in FIG. 7B, the sync area 12 has alength for five periods equal to the length of other areas. In thestructure in FIG. 7C, in order to increase the proportion of the dataarea 13 in the block 11 by decreasing the length of the sync area 12,the wobbling waveforms of the sync area 12 are set as one period, butinstead of this, have a larger amplitude than in FIG. 7B.

Referring to FIG. 4, description will be made of the principle of themethod of detecting address information 13 represented by the wobblingwaveform from the optical disk according to the first embodiment of thepresent invention. To make it easy to understand the principle of themethod of detecting address information according to the presentinvention, description will be made with reference to the waveforms inFIG. 4 which schematically represents signal waveforms. As shown in FIG.5A, the reproducing beam spot is moved along a track, specifically, theland track 271, for example, and a reflected luminous flux is detectedby a two-piece detector 33, whose light receiving face is split in half.As a result, a detection signal of the two-piece detector 33, in otherwords, an output difference signal obtained from the left and rightlight receiving faces of the detector 33 is a composite waveformresulting from algebraically adding together a signal 415 or 416representing the wobbling waveform of the border 15 on the innercircumference side of the land track 271 and a signal 417 or 418representing the wobbling waveform of the border 14 on the outercircumference side of the track 271. The signals 415 and 416respectively correspond to the waveforms representing “0” and “1” on theborder 15 on the inner circumference side. Therefore, the signals 415and 416 are 180 degrees out of phase with each other. Similarly, signals417 and 418 correspond to the waveforms representing “0” and “1” of theborder 14 on the outer circumference side, so that the signals 417 and418 are 180 degrees out of phase with each other. Because the wobblingwaveform of the border 15 on the inner circumference side is 90 degreesout of phase with the wobbling waveform of the border 14 on the outercircumference side, in other words, because the two waveforms are formedso as to be orthogonal to each other, the signals 417, 418 areorthogonal to the signals 415, 416.

According to the present invention, synchronous detection is performedby generating a reference signal 420 for use in detecting signals 415,416 of wobbling waveforms on the border on the inner circumference sideof the track, and a reference signal 421 for use in detecting signals417, 418 of wobbling waveforms on the border on the outer circumferenceside of the track. The reference signals 420, 421 are orthogonal to eachother. By using a fact that the signals 417, 418 on the outercircumference side are orthogonal to the signals 415, 416 of wobblingwaveforms on the border on inner circumference side, the signals 415,416 of wobbling waveforms on the border on the inner circumference sideand the signals 417, 418 of wobbling waveforms on the border on theouter circumference side are separated and detected from a detectionsignal in the form of a composite waveform. The reference signals 420,421 are generated by a method, which will be described later, usingsignals from the sync area 12 on the optical disk 4.

To begin with, a detection signal and two reference signals 420, 421 aremultiplied respectively and integrated with respect to time. Thedetection signal is multiplied by the reference signal 420 for the innercircumference side, and integrated with respect to time. For the sake ofclarity, the signals 415, 416 from the inner circumference side and thesignals 417, 418 from the outer circumference side are respectivelymultiplied by the reference signal 420, and integrated with respect totime. When the reference signal 420 is multiplied by the signals 417,418 on the outer circumference side, since they are orthogonal to eachother, the multiplication results are as indicated by the signals 424,425, and they are reduced to zero by time integration. Morespecifically, the signals of the wobbling waveform on the outercircumference side of the track are reduced to zero by this process anddisappear. On the other hand, when this reference signal is multipliedby signals 415, 416 on the inner circumference side, since they aresynchronized, the multiplication results are as indicated by signals422, 423. When those signals are integrated, bit “0” becomes a signal ofnegative level and bit “1” becomes a signal of positive level, so thatthe phases of the wobbling waveforms on the border 14 can be convertedto amplitude levels. As described, the detection signal is subjected tosynchronous detection using the reference signal 420, and only theaddress information 13 in the wobbling waveform on the border on innercircumference side can be obtained as amplitude levels.

Similarly, the detection signal and the reference signal 421 for theouter circumference side are multiplied together, and integrated withrespect to time. When the reference signal 421 is multiplied by thesignals 417, 418 on the borders on the outer circumference side, sincethese signals are orthogonal to each other, the multiplication resultsare as indicated by the signals 426, 427, and when they are integratedwith respect to time, they are reduced to zero. In other words, thesignals of the wobbling waveform on the inner circumference side of thetrack become zero and become negligible. On the other hand, when thereference signal 421 is multiplied by the wobbling waveforms 415, 416,since these signals are synchronized, the multiplication results becomesignals 428, 429, and when integrated, bit “0” becomes a signal ofnegative level, and bit “1” becomes a signal of positive level, thephases of the wobbling waveforms on the border can be converted intoamplitude levels. As has been described, when the detection signal issubjected to synchronous detection by the reference signal 421, only theaddress information 13 in the wobbling waveform on the outercircumference side can be detected as amplitude levels.

By those processes, address information 13 recorded on the borders onthe inner circumference side and outer circumference side of the trackcan be separated and obtained. By comparing the respective items ofaddress information, it can be accurately known whether the reproducingbeam spot is located on the groove track 270 or 272, or on the landtrack 271, or on which track, 270, 272, or 271, the beam spot islocated.

The configuration of the whole recording and reproducing apparatus forreading address information according to the above-mentioned principlewill now be described with reference to FIGS. 5A, 5B, 28, and 29.

The recording and reproducing apparatus according to the firstembodiment includes an optical disk 4, an optical head 1292, an electriccircuit system, and a drive system as shown in FIG. 29. The optical head1292 incorporates an optical system for recording and reproducing datafrom the optical disk 4 (FIG. 28). The drive system includes a spindlemotor 1290 for rotating the optical head 1292, a tracking actuator 1291a for driving the laser beam 31 in the width direction of the track, anda focus actuator 1291 b for driving the laser beam 31 in the opticalaxis direction. The electric circuit system includes a signal processingsystem for supplying a signal to be recorded on the optical disk 4 tothe optical head 1292, and processing a signal read out from the opticaldisk 4, and a control system for controlling the drive system.

The optical disk 4 according to the first embodiment is 120 mm indiameter, and has two, front and rear substrates glued together. Arecording film 11 is placed between the two substrates. The substrate 10on the side on which a light beam from the optical head 1292 isirradiated is made of plastic 0.6 mm in thickness. Information isrecorded and reproduced by condensing and passing the laser beam 31through the substrate 10. On the surface of the recording film 11 on thesubstrate 10, there are provided groove tracks such as 270, 274, andland tracks such as 271 formed between the groove tracks such as 270,272 as mentioned above. A track pitch 280 is defined as the spacebetween the groove tracks, such as 270, and is 1.2 um in this firstembodiment. The recording film 11 is a film chiefly composed of Ge andis about 300 Angstrom in thickness, and formed on the substrate 10 byvapor deposition. The information mark 274 is an area having a differentreflectance factor from that of the surrounding area and formed byirradiating a laser beam 31 from the optical head 1292 onto therecording film 11 through the substrate 10, to thereby cause a thermalchange on the recording film 11.

The optical head 1292, as shown in FIG. 28, includes a semiconductorlaser 281 for emitting a laser beam 31, and a collimator lens 282, agalvano mirror 283, and objective lens arranged in succession along theoptical path of the laser beam 31 emitted from the semiconductor laser281. Arranged between the collimator lens 282 and the galvano mirror 283is a beam splitter 32 for separating the beam (of the laser beam 31)reflected by the optical disk 4 from the laser beam 31. The reflectedbeam separated by the beam splitter 32 is divided by another beamsplitter 284 into two luminous fluxes. An analyzer 286, a collectivelens 287, and a photodetector 288 are arranged on the optical path ofone luminous flux, and those elements constitute an information markdetecting optical system for detecting the information marks 274. Theother luminous flux, after being condensed by the collective lens 289,is further separated by another beam splitter 285 into two luminousfluxes, and on the optical path of one luminous flux, there are arrangeda cylindrical lens 290 and a four-piece divided detector 291, whichconstitute a focus error signal detecting optical system for detecting afocus error signal representing an extent of shift of the optical disk 4from the focus of the objective lens 34. On the optical path of theother luminous flux separated by the beam splitter 285, the two-piecephotodetector 33 is arranged. The detection signal of the two-piecephotodetector 33 is used for detection of address information 13represented by the wobbling of the borders, such as 14, of the tracks,such as 270, and also for detection of a track shift signal.

The output power of the semiconductor laser 281 is about 35 to 40 mWwhen recording the information marks 274 on the optical disk 4, or about3 to 5 mW when reproducing the information marks 274 and the addressinformation 13 from the optical disk 4.

Description will now be made of the operation of each element whenreproducing information from the optical disk 4. The laser beam 31emitted from the semiconductor laser 271 is collimated by the collimatorlens 282, and then deflected by the beam splitter 32, and furtherdeflected by the galvano mirror 283, and condensed by the objective lens34 to form a reproducing beam spot 1 on the optical disk 4 as shown inFIGS. 5A and 28. FIG. 5A shows the shape of the recording film 11 whenthe optical disk is seen from the side of the substrate 10, andtherefore in FIG. 5A, the shapes of the grooves and lands of the tracks,such as 270, are inverted.

The reflected beam of the laser beam 31 from the optical disk 4 againpasses through the objective lens 34, is reflected by the galvano mirror283, passes through the beam splitter 32, and is separated by the beamsplitter 284 into two fluxes. One luminous flux is condensed as itpasses through the analyzer 286 and the collective lens 287, anddetected by the photodetector 288. Output of the photodetector 288 isprocessed by an electric circuit to be described later, so that signalsfrom the information marks 274 are detected. The other luminous fluxseparated by the beam splitter 284, after being condensed by thecollective lens 289, is separated by a beam splitter 285, and oneluminous flux is condensed by the cylindrical lens 290, and detected bythe four-piece photodetector 33. Output of the photodetector 33 isprocessed by a well-known astigmatism process to obtain a focus errorsignal.

The other luminous flux separated by the beam splitter 285 is detectedby the left and right light receiving faces of the two-piecephotodetector 33. The parting plane of the photodetector 33 is parallelwith the longitudinal direction of the groove track 270. The signals ofthe left and right receiving faces of the two-piece photodetector areinput into a differential detector 38 and an adder 40. Output of thedifferential detector 38, like a signal 521 in FIG. 21, is in a shapeformed by superimposition of signals from wobbling of the borders 14,15of the tracks 270, etc. on the track shift signal. Therefore, a bandfilter 39 is used to pass only the oscillation frequency of the signalsfrom wobbling of the borders 14, 15 of the tracks 270, etc. for inputinto synchronous detectors 42, 43. On the other hand, output of theadder 40 is input to a synchronous signal generator 41 to generatereference signals 420, 421 in FIG. 4.

More specifically, the synchronous signal generator 41 generatesreference signals 421, 422 using the circuit in FIG. 5B according to asignal from the sync area 12 of the optical disk 4. For example, if thesync area 12 has prepit marks of a mark string of 51, 52 in FIG. 7A, aprepit mark detecting circuit 46, shown in FIG. 5B, of the synchronoussignal generator 41 detects a signal corresponding to the mark string of51, 52 from output of the adder 40. This sync areas 12, as describedbefore, are provided at fixed intervals on the tracks, such as 270, sothat by using this signal to start the phased locked loop (PLL) 47,clock pulses with a frequency of a specified multiple of the repeatingfrequency of this signal are generated. The sync area 12 is synchronouswith the wobbling frequency of the borders 14,15 of the tracks 270, etc.Therefore, by starting frequency division by a frequency divider 48 instep with clock pulses generated by a PLL 47, the frequency divider 48generates reference signals 420, 421 which are equal both in wobblingfrequency and phase of the wobbling to the borders 14, 15 of the tracks270, etc.

For example, in the optical disk 4 on which the borders 14,15 of thegroove tracks 272, etc. wobble in the wobbling waveforms shown in FIG.23, the output signal (hereafter referred to as a detection signal 231)of the band filter 39 when the reproducing beam spot 1 is scanning thearea 230 enclosed by a dotted line along the groove track 272 is shownin FIG. 24C. The detection signal 231 output from the band filter 39 hasa waveform (FIG. 24C) which is an algebraically added waveform of thewobbling waveform (FIG. 24A) of the inner circumference border 14 of thegroove track 272 and the wobbling waveform (FIG. 24B) of the outercircumference border 15 of the groove track 272. When this detectionsignal 231 is multiplied by a reference signal 420 from the synchronoussignal generator 41 by means of the synchronous detector 42 (FIG. 24D),a waveform shown in FIG. 24E can be obtained. The waveform in FIG. 24Ecan be divided into an in-phase component (corresponding to the innercircumference side wobbling waveform of the groove 2) of the referencesignal 420 and a component orthogonal to the reference signal 420 (thiscomponent corresponds to the wobbling waveform of the border 15 on theouter circumference side of the groove track 272) (FIG. 24F). Therefore,when the waveform of FIG. 24E is integrated by the synchronous detector42, the orthogonal component is reduced to zero, with the result thatonly the in-phase component appears, and in the case of FIG. 24F, theoutput level is on the positive side, and it is found that the signal isbit “1”. Therefore, by comparing the level of output of the synchronousdetector 42 with a predetermined level using a comparator 44 anddeciding whether the output level is positive or negative, it ispossible to detect whether wobbling data of the inner circumference sideborder 14 of the groove track 272 is “0” or “1”, and thus demodulate theaddress information 13.

Similarly, if synchronous detection is performed on the detection signal231 with the synchronous detector 43 by using a reference signal 421which is 90 degrees out of phase with a reference signal 420, aresulting waveform is as shown in FIG. 24G, and if this waveform isanalyzed, a waveform as shown in FIG. 24H is obtained. If this waveformis integrated by the synchronous detector 43, the orthogonal componentis reduced to zero, and only the in-phase component appears. In the caseof the waveform of FIG. 24H, the output level is positive, and a signalof bit “1” is detected. Therefore, by deciding whether the output levelis positive or negative by comparing the output level of the synchronousdetector 43 with a preset level by the comparator 45, it is possible todetect whether the wobbling data of the outer circumference side border15 of the groove track 272 is “0” or “1”, and thus demodulate theaddress information 13. The demodulated address information is sent tothe formatter 1292 (FIG. 29) of the electric circuit system of therecording and reproducing apparatus, and is also sent through an SCSIinterface 1293 to a CPU (not shown) connected with the recording andreproducing apparatus.

Output of the photodetector 288 is amplified by a preamplifier 1294 inFIG. 29, and after passing through a waveform shaping circuit 1295, isinput to reproduction clock generators 1296, 1297 to generate areproduction clock signal. Data discrimination is performed by areproduction and synthesizing circuit 1298 using the reproduction clockand output of the waveform generator circuit 1295, and data consistingof the information marks 274 is demodulated by a demodulator circuit1299. The demodulated data of information marks 274 is sent to theformatter 1292 (FIG. 29) of the electric circuit system of the recordingand reproducing apparatus, and is also sent through the SCSI interface1293 to a CPU (not shown) connected with the recording and reproducingapparatus.

When information is recorded on the optical disk 4, the formatter 1292receives data to record through the SCSI interface from the host unit,data is converted by the modulator circuit 1311 into a modulated signal,and input into a write pulse generator circuit 1312. The write pulsegenerator circuit 1312 generates recording pulses corresponding to theposition to record data on the track of the optical disk 4 in accordancewith a recording clock generated by a frequency synthesizer 1313, andsends the pulses to a laser driver 1314. A write power switching circuit1315 sets laser power for recording at the laser driver 1314. The laserdriver 1314 generates a pulse waveform to drive the semiconductor laser281 from the set laser power and recording pulses. A high frequencysuperimposing circuit 1316 outputs a waveform, formed by superimposing ahigh frequency on the pulse waveform, to the semiconductor laser 281 todrive the laser 281. Output of the semiconductor laser 281 is monitoredby an auto power controller 1317, and fed back to the laser driver 1314.Thus, a laser beam 31 of high energy is irradiated to a desired track,so that the recording film 11 is heated and information marks 274 areformed.

Description will now be made of control of the drive system while datais being reproduced or recorded on the optical disk 4.

Output of the differential detector 38 is input to a circuit (not shown)to detect a track shift signal of the spot of the laser beam 31 by awell-known method, such as the push-pull method, and thereby detect atrack shift signal. Output of the four-piece detector 291 is input to acircuit (not shown) to detect a focus error signal of the spof of thelaser beam 31 by a method, such as the astigmatism method, and therebydetect a focus error signal.

A track shift signal is input to a tracking control circuit 1300, and acontrol signal to drive a tracking actuator 1291 a is generated.According to this signal, the tracking actuator 1291 a moves the galvanomirror 283 to position the sopt of the laser beam 31 along a desiredtrack, such as 270. The focus error signal is input to the focus controlcircuit 1301 to generate a control signal to drive the focus actuator1291 b. In response to this control signal, the focus actuator 1291 bdrives the objective lens 34 in the optical axis direction, and therebyperforms focus servo to maintain focus of the objective lens 34 on thesurface of the optical disk 4.

Access of the spot of the laser beam 31 onto the optical disk 4 isperformed by a fine actuator 1309 for a minute range, but when the beamspot is moved over a long range, the course actuator 1310 is used tomove the whole optical head. During tracking, the fine actuator 1309 andthe course actuator 1310 move in an interlocked motion with each other.Therefore, even if the center of the optical disk 4 deviates from thecenter of the spindle motor 1290 which rotates the optical disk 4, thespot of the laser beam 31 can be made to stably follow the tracks 270,etc.

When giving the spot of the laser beam 31 long-range access to a desiredtrack, the optical head 1292 is moved by the course actuator 1310 over along distance to the vicinity of the track. Then, the beam spot is movedby an interlocked motion of the fine actuator 1309 and the courseactuator 1310 so that the beam spot is positioned at the target track.The series of motions are performed by the actuators 1309, 1310 undercontrol of a mechanical controller 1303 by exchange of information amongthe mechanical controller 1303, the tracking control circuit 1300, andthe course control circuit 1302. The spindle motor 1290 is driven by thespindle motor control circuit 1307 so that the optical disk 4 rotatesstably at a specified number of revolutions.

The whole drive system is controlled by a drive control MPU 1304, andsignals are exchanged among an auto loading mechanism 1308, themechanical controller 1303, and a controller control MPU 1306 etc. Theoptical disk 4 is attached and detached to and from the spindle by theauto loading mechanism 1308 under control of the drive control MPU 1304.Further, the beam spot is positioned for recording and reproduction bycontrolling the mechanical controller 1303, signals are processed forrecording and reproduction by controlling the controller control MPU1306, and maintenance information is obtained by controlling the panelcontrol unit.

Meanwhile, arranged between the formatter 1292 and the SCSI interface1293 are a buffer memory 1318 and a buffer controller 1319. The buffermemory 1318 temporarily stores reproduced data bound for the host unit,and record data to be recorded that is received from the host unit, andthe buffer controller 1319 controls the buffer memory 1318. Thecontroller control MPU 1306, etc. are connected with an ECC circuit 1320for correction of error data.

In the first embodiment, a reproduction clock signal are generated froma signal of the sync area 12, while on the other hand, for the recordingclock signal, a clock signal of fixed frequency output from thefrequency synthesizer 1313 is used, but needless to say, a clock signalgenerated from a signal of the sync area 12 can be used for recording. Avariation occurs in the relative linear velocity of the beam spot on thetrack during recording due to a variation in the number of revolutionsof the optical disk 4 or the eccentricity of the center of the opticaldisk 4 with respect to the rotating center of the spindle motor. Whenthis variation occurs, a recording clock signal generated from a signalof the sync area 12 also varies with this variation, so that by usingthe recording clock signal, information marks 274 can be recorded at afixed frequency on the track.

Description will be made of the optical disk producing method accordingto a second embodiment of the present invention for the optical disk 4according to the first embodiment.

To begin with, the shape of the shape of the tracks, such as 270, on theoptical disk 4, and the shape of the mark string of 51, 52 etc. of thesync area 12 are precisely formed on the surface of a glass substrate ina disk form as shown in FIG. 22, and from this glass substrate, anoriginal disk 68 is formed. The original disk 68 has a photoresist film68 a deposited on a flat glass substrate 68 b (FIG. 6), and patterns oftracks 270, etc. are transferred to the photoresist film 68 a byexposure to light, and the original disk 68 are formed by developing thephotoresist film. The shape of the surface of this original disk 68 istransferred to a metal such as nickel to form a metal stamper. When aplastic substrate 10 is molded by a method such as injection moldingusing this stamper, a plastic substrate 10 having tracks 270, etc. andmark strings, such as 51, 52 of the sync area 12 formed on the surfacecan be produced (FIG. 10). Subsequently, by forming a recording film 11on the plastic substrate 10 by vapor deposition, for example, andattaching another substrate to the substrate 10, an optical disk 4 iscompleted.

At this time, since the optical disk 4 according to the first embodimenthas a structure which represents address information 13 by wobbling theborders 14, 15 of the tracks 270, etc., it is necessary to preciselyform the shapes of the tracks 270, etc. having wobbling waveforms (ofthe borders 14, 15) of desired phase on the surface of the original disk68. Therefore, in this embodiment, by scanning the beam spot 69 whilewobbling in the radial direction of the disk on the disk-shape glasssubstrate 68 b covered on its surface with the photoresist film 68 a,the hatched area in FIG. 22 is exposed to light. The area exposed tolight is removed by a developing process and thereby groove tracks 270,272, etc. are formed. The portion between the adjacent groove tracks270, 271 remains after the exposure, and becomes a land track 271. Thus,an original disk 68 is formed as shown in FIG. 22.

The method of light exposure of the original disk 68 and the lightexposure system used will be described with reference to FIGS. 6 and 8.FIG. 8 shows a light exposure system to be used for exposure of theoriginal disk 68 to light. FIG. 6 shows scanning of the beam spot 69used when the groove tracks 270, etc. are formed on the original disk68. Here, an explanation will be given for the case where the sync area12 recorded on mark strings 51, 52 etc. in FIG. 7A.

In FIG. 8, the beam 64 from the light source 61, after having itsintensity adjusted by the intensity modulator 62, passes through a beamdeflector 63, is reflected by a mirror 66 to the original disk 68, andis condensed by the objective lens 67 to the original disk 68. Thus, aminute beam spot 69 is irradiated to the glass substrate 68 b covered onits surface with a photoresist film 68 a. The beam deflector 63, drivenby a deflector drive circuit 76, minutely oscillates the optical axis ofthe beam 64. Therefore, the beam spot 69 on the original disk 68minutely oscillates in the radial direction of the original disk 68. Theamplitude of the oscillation is the width of the groove tracks 270, etc.If this width of the oscillation is made to vary with the wobblingwaveforms of the borders 14, 15 of the groove tracks 270, etc., lightexposure can be performed in the shape of the groove track 270 whoseborders 14, 15 wobble. In this manner, while the beam spot 69 is made tooscillate, the rotating motor 71 joint to a spindle 70 is driven by amotor drive circuit 72 to rotate the original disk 68. At the same time,a carriage 65 on which a bending mirror 66 and an objective lens 67 aremounted is moved gradually in the radial direction of the original disk68 by a carriage drive circuit 74. The amount of movement of thecarriage 65 is set as the amount of track pitch 280 (FIG. 28) by whichthe center of the beam spot 69 is shifted each time the original disk 68makes a turn. By those motions, the tracks 270, etc. are formed in aspiral form at intervals of the track pitch 280, and the borders 14, 15of the groove tracks 270, etc. can be made to wobble with specifiedphases. The carriage drive circuit 74 and the motor drive circuit 72 arecontrolled with feedback by the address recording control circuit 73.The address recording control circuit 73 sends a deflection signal 104to the deflector drive circuit 76. The address recording control circuit73 sends an intensity modulation signal to a modulator drive circuit 75.

The structure of the address recording control circuit 73 will bedescribed in detail with reference to FIGS. 9A, 9B.

As shown in FIG. 9A, the address recording control circuit 73 includesan address signal generator 92, and a reference clock circuit 95 foroutputting a reference clock signal. Moreover, the address recordingcontrol circuit 73 includes an intensity signal generator 90 foroutputting an intensity signal 105 to the modulator drive circuit 75,and a deflection signal generator 91 for generating a deflection signal104, a head position control circuit 93 for outputting a signal tospecify a drive amount to the carriage drive circuit 74, and a rotationcontrol circuit 94 or outputting a signal to specify a drive amount tothe motor drive circuit 72.

The address signal generator 92 receives rotation information 79 showingthe current number of revolutions from the rotating motor 71 togetherwith movement information 78 showing the current position from thecarriage 65, and generates a head command signal showing a drive amountof the carriage 65 to make groove tracks 270, etc. in a spiral form. Thehead position control circuit 93 compares a head command signal with themovement information 78, and outputs a signal to control the carriage 65to the carriage drive circuit 74. The address signal generator 92obtains a number of revolutions corresponding to the position of thetrack 270, for example, by using rotation information 79, and outputsthis number as a rotation command signal to the rotation control circuit94. The rotation control circuit 94 compares rotation information 79with the rotation command signal, and controls the rotating motor so asto rotate at a specified number of revolutions corresponding to theposition of the head.

The address signal generator 92 generates an address signal showing theaddress of the groove track 270, for example, on the basis of rotationinformation 78 and movement information 79, and outputs the addresssignal to the deflection signal generator 91. Furthermore, the addresssignal generator 92 generates a clock signal 103 (FIG. 10) by dividingthe frequency of the reference clock from the reference clock circuit95, and outputs the clock signal to the deflection signal generator 91.From those signals, the deflection signal generator 91 generates adeflection signal 104 (FIG. 10) using a circuit to be described later.In addition, the address signal generator 92 generates an intensitycommand signal. On the basis of the intensity command signal, theintensity signal generator 90 generates an intensity modulation signal105 (FIG. 10) to modulate the intensity of the beam 64 to form marks 51,52, etc. in the sync area 12. To have the marks 51, 52 of the sync area12 formed such that they wobble to right and left from the center of thetrack, the address signal generator 92 generates and outputs asynchronous area command signal to the deflection signal generator 91.

The structure of the deflection signal generator 91 and the method ofgenerating a deflection signal 104 will be described with reference toFIG. 9B. An address signal is input to an address modulator 96,generates an address of the inner circumference side border 14 of thegroove track 270, e.g., a signal of “110”, and an address of the outercircumference side border 15, e.g., a signal of “110”. The two addressesare converted by the phase modulator circuit 97 into wobbling waveformsrepresenting “1” and “0” according to a difference of the phase as shownin FIG. 3, thus forming an amplitude signal 100 corresponding to theaddress of the inner circumference side border 14 and an amplitudesignal 101 (FIG. 10) corresponding to the address of the outercircumference side border 15. Those signals are input to the deflectionsignal generator 98. A clock signal 103 is input to a scan signalgenerator 99, which generates a scan signal 102 for scanning the beamspot 69 in the radial direction of the original disk 68, and outputs thescan signal to the deflection signal generator 98. The deflection signalgenerator 98 generates a deflection signal (FIG. 10) by modulating theamplitude of the scan signal 102 by using the amplitude signal 100 andthe amplitude signal 101 so that the beam spot 69 scans between theinner circumference side border 14 and the outer circumference sideborder 15. The synchronous area command signal is input to thedeflection signal generator 98. The deflection signal generator 98generates a deflection signal 104 to cause the beam spot 69 to deflectin synchronism with the scan signal 102 in the sync area 12 so as toshift about ¼ of the track pitch 280 to the left and right of the groovetrack, such as 270.

By using a deflection signal 104 designed to work as mentioned above, byperforming the light exposure process on the original disk 68 with thelight exposure system in FIG. 8, the shape of the groove track 270, forexample, showing address information in wobbling waveforms of theborders 14, 15 and the shape of the mark strings 51, 52 in the sync area12 in FIG. 7A are exposed to light. Therefore, by perfroming thedeveloping process on the original disk 68, the original disk 68 for theoptical disk 4 according to the second embodiment can be produced.

In the above description, the exposure method was discussed referring tothe case of the sync area 12 in FIG. 7A, but the other forms of syncarea 12 shown in FIGS. 7B and 7C can also be formed by exposure.However, in the cases of FIGS. 7B and 7C, since the sync area 12 isformed by grooves, the deflection signal 104 is made so that the syncarea 12 is exposed to light in a shape of a groove.

Description will next be made of the method and the circuit forreproducing address information according to a third embodiment of thepresent invention. This detection method reproduces address information13 from the optical disk 4 without using the sync area 12.

In the optical disks having the sync area 12 as shown in FIGS. 7A, 7Band 7C, information marks 274 cannot be recorded in the sync area 12,and the sync area 12 occupies that portion of the track. If referencesignals 420, 421 and a reproducing clock signal can be detected from thewobbling waveforms of the borders of the tracks 270, etc., there is noneed to provide the sync area 12, and the data recording efficiency canbe improved.

According to the third embodiment, in place of the sync area 12, asynchronous (SYNC) segment is provided which has the same phase as thewobbling waveforms of the inner circumference side border 14 and theouter circumference side border 15 of the track. The SYNC segment islike the sync area 12 of FIG. 7B, but as shown in FIG. 7B, the wobblingamplitude of the sync area 12 is made larger than the wobbling amplitudeof the address information 13, and therefore information marks 274cannot be recorded in the sync area 12, but the SYNC segment is set tohave the same wobbling amplitude as in address information 13.Therefore, information marks 274 can be recorded in the SYNC segment inthe same way as in other areas.

Referring to FIG. 11, description will start with the method ofgenerating reference signals 420, 421 from an optical disk 4 accordingto the third embodiment without using the sync area 12. As describedabove, in address information 13, the wobbling waveforms of the borders14, 15 of the tracks 270, etc. have the same frequency, but differ inphase. The phase differences take no more than four states: 0 degree, 90degrees, 180 degrees, and 270 degrees, so that timing at zero crossingof the detection signal 231 (FIGS. 5 and 24) when the wobbling of agroove is detected corresponds to 4t (t is a natural number) times thefrequency of the wobbling. Accordingly, the circuit structures of FIGS.5A and 5B are changed into those in FIGS. 11A and 11B, and the timing atzero crossing of the detection signal 231 is detected by a zero crossdetector 125, and in synchronism with the timing, a PLL (phase lockedloop) 126 is started. By this arrangement, a signal having a frequencyfour times the wobbling frequency can be produced. What is more, if therelative linear velocity between the reproducing and recording beam spot1 and the track 270 varies due to a minute variation in the rotatingspeed of the spindle motor 1290 (FIG. 29) or the eccentricity of theoptical disk 4 with respect to the rotating center of the spindle motor1290, the signal produced as mentioned above also varies with thosevariations. Therefore, this signal is synchronous with the recordedwobbling waveform, and by dividing the frequency of this signal by afrequency divider 127, a synchronous signal of a wobbling waveform withthe same frequency as the recorded wobbling waveform can be obtained.

The synchronous signal of the frequency-divided wobbling waveforms has afrequency synchronous with the wobbling waveforms, but it is not knownwhether the phase is synchronous with the wobbling waveforms. Togenerate reference signals 420, 421, it is necessary to provide asynchronous signal synchronous in phase with the wobbling waveforms, sothat this phase needs to be decided. To this end, the frequency divider127 is used to generate signals having four phases, 0 degree, 90degrees, 180 degrees and 270 degrees on the basis of output of the PLL126. Any one of those signals is in phase with the wobbling waveforms.The above-mentioned SYNC segment is used to select the synchronizedphase out of the four phases.

Out of detection signals 231, a detection signal 231 from ordinaryaddress information 13 and a detection signal 231 from the SYNC segmentare separated by using a sync detection circuit 133. Specifically, witha detection signal 231 of ordinary address information 13, regardless ofwhat phase the detection signal 231 has, both synchronous detectors 42,43 provide a positive or negative level of output. However, on the SYNCsegment, only one of the synchronous detectors 42, 43 provides apositive or negative level of output, and the other detector provideszero output. Therefore, since level decision circuits 123,124 identifythe area where either one of outputs of the synchronous detectors 42,43becomes zero, the SYNC segment can be detected. FIG. 12 shows detail ofthe level decision circuits 123,124. A signal from synchronous detector42 is compared with a positive level v1 and a negative level v2 bycomparators 226, 227, 228, and 229 in the level decision circuits123,124. If output of the synchronous detector 42 is larger than v1, alevel “1” signal synchronous with the reference signal 420 appears at anoutput signal 206 of a flip-flop 200. If output of the synchronousdetector 42 is between v1 and v2, in other words, if output of thesynchronous detector 42 is close to zero, a level “1” signal synchronouswith the reference signal 420 appears at a signal 205 after passingthrough flip-flops 202, 203, and an AND circuit 201. Similarly, ifoutput of the synchronous detector 42 is smaller than v2, a level “1”signal appears at a signal 207 from a flip-flop 204.

The detailed operation of the level decision circuit 123 has beendescribed. Similarly, in the level decision circuit 124, if output of asynchronous detector 43 is larger than v1, a level “1” signalsynchronous with the reference signal 421 appears at a signal 218. Ifoutput of the synchronous detector 43 is between v1 and v2, a signal “1”signal synchronous with the reference signal 421 appears at a signal219, and, if output of the synchronous detector 43 is smaller than v2, alevel “1” signal appears at a signal 220.

Signals 206, 207 or signals 218, 220 showing if output is larger than v1or smaller than v2 are ORed by the logical OR circuits 208, 216. Theresults of these logical operations and signals 205, 219 showing zero ofthe decision circuits 123, 124 are ANDed by the logical AND circuits209, 217. When the results of those logical operations are ORed by thelogical OR circuit 210, a sync signal 121, which shows that thedetection signal 231 is a signal from the SYNC segment, can be obtained.

When the SYNC segment is detected as mentioned above, signals forreference signals 420, 421 can be selected from the signals with fourphases mentioned earlier, using the detection signal 231 from the SYNCsegment.

Description will be made of the principle for selecting signals for thereference signals 420 421 from signals with four phases. Since thereference signal 421 is 90 degrees out of phase with the referencesignal 420, if the phase of the reference signal 420 is decided, itfollows that the phase of the reference signal 421 can be decided. Oneof the signals of four kinds of phases 0 degree, 90 degrees, 180 degreesand 270 degrees generated by the frequency divider 127, to take anexample, a signal with the phase of 0 degrees is input from thesynchronous signal generator 41 into the synchronous detector 42 as areference signal 420. A signal 90 degrees out of phase with thereference signal 420, that is, a signal of a phase of 90 degrees isinput to the synchronous detector 43 as a reference signal 421. Sincethe SYNC segment is formed such that the wobbling waveform of the innercircumference side border 14 and the wobbling waveform of the outercircumference side border 15 are in phase with each other, either one ofthe outputs of the synchronous detectors 42, 43 in FIG. 5A in relationto the SYNC segment is zero, and the other output becomes a positive ora negative level. At this time, there are two factors for deciding ifeither one of outputs is zero, positive or negative: one is the phase ofthe wobbling waveform in the SYNC segment and the other is the positionat which the reproducing beam spot 1 is located, i.e. the groove tracks,270, etc. or the land tracks 271, etc.

Accordingly, since the wobbling waveform of the SYNC segment is alreadyknown, by selecting a groove track 270 or the like or a land track 271or the like, by positioning the beam spot at the selected track usingthe tracking control system 132 and the tracking polarity switchingcircuit 130 included in the tracking control circuit 1300, and byknowing which of the outputs of the synchronous detectors 42, 43 is 0,it can be decided whether the phase relationship between the referencesignal 420 which was input and the reference signal 420 to be input is 0degrees or 180 degrees, or 90 degrees or 270 degrees.

For example, when the phase relationship is known to be 0 or 180 degreesby the above decision, by further detecting if a non-zero output fromthe outputs of the synchronous detectors 42, 43 is positive or negative,a further decision can be made as to whether the phase relationship is 0degrees or 180 degrees. Similarly, if the phase relation is known to be90 degrees or 270 degrees by the above decision, a further decision canbe made as to whether the phase relationship is 90 degrees or 270degrees.

The above-mentioned decisions can be made by a circuit block as shown inFIG. 12. In FIG. 12, the switching command circuit 131 is a part of themechanical controller 1303, and switches over the selection of thegroove track, such as 270, or the land track, such as 271. The logicalAND operations are carried out by AND circuits 212, 213, 214 and 215between, on one hand, a signal 225 of a polarity which indicates whetherthe track, such as 270, selected by the switching command circuit 131 isa groove or a land, and, on the other hand, signals 206, 207, 218, and220 showing the synchronous detector output level being larger than v1or smaller than v2, as detected by the level decision circuits 123 and124. Note that one of the signals with four kinds of phases of 0degrees, 90 degrees, 180 degrees, and 270 degrees, produced by theabove-mentioned frequency divider 127, that is, a signal of a phase of 0degrees, for example, is input as a reference signal 420 from thesynchronous signal generator 41 to the synchronous detector 42. As thereference signal 421, a signal which is 90 degrees out of phase with thereference signal 420 is input to the synchronous detector 43.

In the circuit of FIG. 12, when the reference signal 420 currently beinginput is 0 degree out of phase (in other words, in synchronism) with acorrect signal which should have been input as the reference signal 420,the signal 221 is at the level of “1”, or when the phase difference is90 degrees, the signal 222 is at the level “1”, or when the phasedifference is 180 degrees, the signal 233 is at “1”, or when the phasedifference is 270 degrees, the signal 224 is at “1”. Thus, in the phasecommand signal 120 consisting of signals 221 to 224, by detecting whichsignal is at the level “1”, a decision can be made as to how the phaseof the reference signal 420 currently being input is shifted from thephase of a reference signal 420 which is correct and should have beeninput.

By inputting the phase command signal 120 into the selector 128 andhaving the selector 128 select any of the four signals with differentphases, which are generated by the phase divider 127, a correctreference signal 420 can be selected. For example, when the signal 222which is 90 degrees out of phase with a correct phase is at the level“1” in the phase command signal 120, the selector 128 selects a signalformed by adding a phase of 270 degrees to the reference signal 420currently being input, and the synchronous detector 42 outputs thissignal as the reference signal 420. On the other hand, as the referencesignal 421, a signal obtained by adding 90 degrees to the referencesignal 420 is output.

Thus, reference signals 420, 421 can be formed from the wobblingwaveform detection signal 231 of the borders 14,15. The referencesignals 420, 421 vary in accordance with variation in the linearvelocity of the reproducing beam spot on the tracks 270, etc. due to thevariation in the number of revolutions of the current optical disk 4 orthe eccentricity of the optical disk 4, and so on. Therefore, by usingthe reference signals 420, 421, the information marks 274 and theaddress information 13 can be accurately demodulated.

Description will now be made of the method of generating a recording anda reproducing clock signal used when recording and reproducing data fromthe wobbling waveforms of the borders 14, 15 on the tracks 270, etc.Applied to this method is the fact that the oscillation frequency of PLL126 in FIG. 11 is 4t times the wobbling frequency as described above.More specifically, the oscillation frequency of PLL 126 is multiplied bya specified number. For example, if the wobbling frequency of theborders 14, 15 is set at 7.5 kHz or so and the frequency of a recordingor reproducing clock signal is set at 7.5 MHz, then the oscillationfrequency of the PLL 126 is 4t times the wobbling waveforms, namely, 150kHz. By multiplying this 150 kHz by a specified number (e.g., 50), arecording signal or a reproducing clock signal can be produced. Whenthis recording or reproducing clock signal is used, even if the linearvelocity of the recording and reproducing beam spot 1 on the tracks 270,etc. varies due to a minute variation in the number of revolutions ofthe optical disk 4, and the eccentricity of the optical disk 4,information marks 274 can be recorded and reproduced.

Subsequently, description will be made of the method of reproducingaddress information 13 and the circuit structure for reproductionaccording to a fourth embodiment of the present invention.

In the third embodiment of the present invention, it is necessary todecide the phases of the reference signals 420, 421 for use in detectingaddress information 13, but in the fourth embodiment, addressinformation is detected without deciding the phases.

In the fourth embodiment of the present invention, a composite waveformof the waveforms of the inner circumference side border 14, and theouter circumference side border 15 of each track 270, for example isdetected for each bit. When recording address information 13, in otherwords, when tracks are formed on the original disk 68 by the lightexposure process, it is arranged that the phase of the compositewaveform of the subsequent bit is shifted by an amount decided by apredetermined rule from the phase of the preceding bit, and addressinformation 13 is recorded utilizing the phase difference between thecomposite waveforms. The actual wobbling waveforms of the borders 14,are formed as waveforms obtained by decomposing the composite waveform.When reproducing address information 13, the phase of the compositewaveform of each bit is detected, and a phase difference from thepreceding bit is obtained by using the differential detector 38, and theband filter 39. By collating the obtained phase difference with theabove-mentioned rule, address information is reproduced.

Description of this will now be given in more detail. Data “1” and “2”represented by the borders 14, 15 of the tracks 270, etc. are combinedto form pairs of data of the inner circumference side border and data ofthe outer circumference side border. The result is that data of a givenbit is any one of the following four cases: a case of “0” on the innercircumference side border and “0” on the outer circumference sideborder; a case of “0” on the inner circumference side border and “1” onthe outer circumference side border; a case of “1” on the innercircumference side border and “0” on the outer circumference sideborder; a case of “1” on the inner circumference side border and “1” onthe outer circumference side border. The phases of the compositewaveforms differ among all of the above fours pairs. In the fourthembodiment, by using this, in relation to the phase of the compositewaveform of the preceding bit, the degree of shift in the phase of thecomposite waveform of the next bit is set for various pairs of thecomposite waveforms arranged in a row. The phase differences and thecorresponding pairs of the composite waveforms are formulated as a rule.

FIG. 14A is an example of the rule. To be more specific, when data “0”is recorded at the inner circumference side border and data “0” at theouter circumference side border at a given bit, the phase of thecomposite waveform for this bit is set to be the same as the phase ofthe composite waveform of the preceding bit. Alternatively, when data“0” is recorded at the inner circumference side border and data “1” atthe outer circumference side border, the phase of the composite waveformof this bit is set to lead π/2 rad on the phase of the compositewaveform of the preceding bit. When data “1” is recorded at the innercircumference side border and data “0” at the outer circumference side,the phase of the composite waveform of this bit is set to lead π rad onthe phase of composite waveform of the preceding bit. When “1” isrecorded at the inner circumference side border and “1” at the outercircumference side border, the phase of the composite waveform of thisbit is set to lead 3 π/2 rad on the phase of the composite waveform ofthe preceding bit.

When an original disk 68 is prepared, the phase of the compositewaveform representing data of address information is obtained accordingto this rule, and by decomposing this composite waveform, the wobblingwaveforms of the borders 14, 15 are determined. As has been describedwith reference to FIGS. 24A, 24B and 24C, the detection signal 231 (FIG.24C) output from the band filter 39 is a composite waveform of thewobbling waveform of the inner circumference side and the wobblingwaveform of the outer circumference side of the track. Therefore, bydetecting the amount of shift of the phase of the detection signal 231from the preceding bit, data of the inner circumference side border anddata of the outer circumference side border can be reproduced togetheras a combination of data only from the phase difference.

However, since data of the border is shared by the groove track, such as270, and the land track, such as 271, if data is to be recordedaccording to the above rule in a combination of the inner circumferenceside border 14 and the outer circumference side border 15 of the groovetrack side 270, it is impossible to record data of the same bit on theland track side 271 because of the above rule. Therefore, as indicatedby the broken line in FIG. 14B, the inner and outer borders are combinedin a pair 1402 of the groove track side 270 etc. and the land track side271 etc. at every other bit. Like the SYNC segment in the precedingembodiment, synchronous segments 1401, by which the phases of the innercircumference side border and the outer circumference side border arematched, are provided at fixed intervals. When reproducing the compositewaveform of the pair 1402, this synchronous segment 1401 is detected,and by counting down the clocks on the basis of this synchronoussegment, signals indicating the bit areas are formed, and by using thebit indication signals, the pair 1402 on the groove track, such as 270,and the pair 1402 on the land track, such as 271, are separated anddetected.

Description will be continued with reference to an illustrative example.For example, as shown in FIG. 19, data “0” or “1” of address information13 is going to be recorded at the borders of the tracks. Supposing thatdata at the inner circumference side border 14 of the groove track 270is denoted by A, and data at the outer circumference side border 15 isdenoted by B, then the first bit is (0, 0) for (A, B). Suppose that (1,0) is going to be recorded at the next bit. In this case, it isnecessary to record a composite waveform which is by π out of phase withthe composite waveform of the preceding bit. Accordingly, if the phaseof the composite waveform of the preceding bit (0, 0) is 0, the phase ofthe composite waveform of bit (1, 0) is π, so that the phases of thewobbling waveforms of each border are as shown in FIG. 19. If (0, 1) isrecorded next to (1, 0), it is required to record a composite waveformwhich is π/2 out of phase with the composite waveform of the precedingbit. Hence, the phases of the composite waveform of bit (0, 1) and thewobbling waveforms of the borders are as shown in FIG. 19. After this,by deciding the phases of the composite waveforms, the phases of thewobbling waveforms of the borders can be decided.

Meanwhile, in reproduction, like in the preceding embodiment, a clocksignal is generated which has a frequency four times the wobblingfrequencies of the borders 14, 15 of the track, and by dividing thefrequency of the clock signal, reference signals 420, 421 forsynchronous detection are produced. The phase may take four states, butany phase may be used. The reason for this is as follows. The reason forthis is that, since data can be reproduced only from the phasedifference of the composite waveform, the only thing required first ofall is to find the phase of the composite waveform of the first bit, andthereafter data can be reproduced using a difference from the precedingbit. In this case, if the phases of the reference signals 420, 421 arenot selected correctly, data at the first bit cannot be read correctly,but from the next bit onward correct data can be reproduced. Becauseaddress information 13 can be recorded repeatedly at the borders of onetrack 270, for example, there is no problem even if data at the firstbit cannot be read correctly. By performing synchronous detection byvarying the phases of the reference signals 420, 421 according to dataof reproduced address information 13, it is possible to generatereference signals 420, 421 of correct phases on the basis of the phaseof the previous data.

FIGS. 15 and 16 are circuit block diagrams for demodulating address dataaccording to the address information reproducing method mentioned above.The synchronous segment detection circuit 333, just as in sync signaldetection by the detection circuit 133 in the third embodiment, detectsthe synchronous segment 1401, and outputs a synchronous segment signal121′ in FIG. 13. The synchronous sync detection circuit 333 generates agroove/land modulator signal 326 from a signal which has detected thesynchronous segment 1401. The groove/land modulator signal 326 is amodulation signal to indicate whether the pair 1402 for a bit is on thegroove track, such as 270, or on the land track, such as 271. Those twosignals are input to the address demodulator circuit 422, and are usedas timing signals in demodulating data. The address demodulator 422 areceives outputs from the synchronous detectors 42, 43 in the form ofbinary signals to which those outputs have been converted by thecomparators 44, 45. The address demodulator 422 a, according to timingcontrolled by the synchronous segment signal 121′ and the groove/landmodulator signal 326, separates address information of a data pair at agroove track, such as 270, and a data pair at a land track, such as 271,to thereby reproduce (demodulate) data according to the above-mentionedrule.

Description will now move on to the detailed circuit structure and theoperation of the synchronous detection circuit 333. As has beendescribed, the synchronous detection circuit, using the same circuitstructure and operation as in the sync detection circuit 133, generatesa synchronous segment signal 121′ shown in FIG. 16. The synchronousdetection circuit 333 divides the frequency of the clock signal in thecounter 340 of the data timing generator 325 by using the synchronoussegment signal 121′ and the clock signal 400 to thereby generate asignal 350 (FIG. 13) corresponding to bit periods, and subdivides thesignal 350 by half, and generates a groove/land modulator signal 326 insynchronism with the synchronous segment signal 121′. The synchronousdetection circuit 333 generates signals to detect the phases of thecomposite waveforms of each bit by performing logical operations at thecircuits 208, 209, 210, 216, 217, 312, 313, 314, and 315 using binarysignals 205, 206, 207, 218, 219, and 220 converted from outputs of thesynchronous detectors 42, 43. The synchronous segment detection circuit333 associates the outputs of the AND circuits 312, 313, 314, and 315with four kinds of data of the pairs 1402, and inputs the results tomemories 327, 328, 329 and 330. The memories 327, 328, 329 and 330 storethe phases of the pairs 1402 on the groove tracks, such as 270, and thephases of the pairs 1402 on the land tracks, such as 271, and reads outthe preceding phase when data of the next pair on the same track isdemodulated.

The detailed structure of the memories 327 to 330 will be described withreference to the memory 327 as an example. The memory 327 takes theoutput of the AND circuit 312 into the flip-flop circuits 341 and 343respectively at the leading edge of the groove/land modulator signal 326and at the leading edge of the inverted signal of the groove/landmodulator signal 326, and sends out the output as it is selected by theselector 342 according to the polarity of the groove/land demodulatorsignal 326. The output of the memories 327, 328, 329, and 330 is used asa phase command signal 320 to select signals of correct phases bycontrolling the selector 428 to produce reference signals 420, 421 ofcorrect phases.

Description will be made of the method of reproducing addressinformation 13 and the circuit structure for reproduction according to afifth embodiment of the present invention.

In the preceding embodiment, data on both borders 14, 15 of each track,such as 270 is recorded and reproduced as data in a pair 1402 for everybit. In the fifth embodiment of the present invention, data on theborders 14, 15 of a track, such as 270, is independently modulated andrecorded. To be more specific, data for a bit on the inner circumferenceside border 14 of a track 270, for example, is recorded by a phasedifference with respect to the wobbling waveform of data at thepreceding bit. The phase differences with respective pieces of datashould be decided as a rule in advance as shown in FIG. 17A. The rule inFIG. 17A is as follows: When data at the next bit is “0” on a certainborder 14, or 15 regardless of whether data at the preceding bit is “0”or “1”, a wobbling waveform of the same phase as in the wobblingwaveform at the preceding bit should be set, and when data at the nextbit is “1”, a wobbling waveform of a phase leading by π on the phase ofthe wobbling waveform at the preceding bit should be set. When data isrepresented with a phase difference of a wobbling waveform for eachborder 14, if it is clear which of outputs of the synchronous detectors42, 43 is data on the inner circumference side border of a track, suchas 270 and which of outputs is data on the outer circumference sideborder, then separate items of data which correspond to the synchronousdetectors 42, 43 can be detected even though the phases of the referencesignals 420, 421 are 180 degrees out of phase with each other.

Note that the SYNC segments having the same wobbling waveform on theinner and outer circumference side borders are provided at fixed periodsalso in this fifth embodiment.

In order to decide which of the synchronous detectors 42, 43 outputsdata on the inner circumference side of the track and which of thosedetectors 42, 43 outputs data on the outer circumference side of thetrack, it is only necessary to use the methods of sync detection andphase decision of the reference signals described with reference toFIGS. 11 and 12. In other words, since the phase of the wobblingwaveform in the SYNC segment has already been decided, and depending onwhether the location of the beam spot 1 is on a groove track or on aland track, the polarity of outputs of the synchronous detectors 42, 43is detected when the phases of the reference signals 420, 421 are zero.Therefore, by detecting the polarity of the level of output of thesynchronous detectors 42, 43, the phases of the reference signals 420,421 can be decided correctly.

In the fifth embodiment in FIG. 17, instead of the above-mentioned SYNCsegment or synchronous segment 1401, data for synchronization may berecorded at fixed periods on both borders 14, 15. For example, as shownin FIG. 18A, two synchronous bits 1811 are secured in fixed periods, inwhich data “01” is recorded, for example, to show that those two bitsare for synchronization purpose. By this arrangement, the sync bits 1811can be detected regardless of the state of phase by the same detectionprinciple as in the embodiment in FIG. 17. The frequency of the timingsignal for detecting the sync bits 1811 may be divided to generate areproducing clock signal or a recording clock signal. When output of thesynchronous bits 1811 is zero, the area where output of the synchronousdetector 42 or 43 is zero is detected by the level decision detectors,so that the uncertainty of the phases of the reference signals 420, 421is reduced by half. In other words, it is known which side the track thesynchronous detectors 42, 43 correspond to, the inner circumference sideor the outer circumference side. Also in the fifth embodiment in FIG.17, as shown in FIG. 18B, like in the case of the synchronous segment1401, by inserting bit 1812 of a predetermined phase at fixed intervalsin data, a reproducing clock signal or a recording clock signal can begenerated from a signal of this bit 1812. In addition, timing by whichto correctly set the phases of the reference signals 420, 421 isincreased, so that recovery from loss of synchronism can be achievedquickly, thereby enhancing reliability.

Finally, description will be made of a sixth embodiment of the presentinvention.

In this embodiment, the method of detecting a track shift signal withoutoffset will be discussed.

When the reproducing beam spot goes across a track, output of thedifferential detector 38, shown in FIG. 20, which has a similar circuitstructure as in FIG. 5A is represented by the signal 521 in FIG. 21,having a wobbling frequency component (the dotted line) superimposed onthe track shift signal (the solid line). At this time, as the center ofthe beam on the two-piece detector 33 of FIG. 5A deviates from the splitcenter of the two-piece detector 33, offset occurs in the signal 512 ofFIG. 21, and the position of the zero point of the track shift signalshifts from the center of the track, such as 270. Only the wobblingfrequency component is extracted from the signal 521 by the band filter39, then signals 522 and 523 are obtained as outputs of the synchronousdetectors 42, 43. Specifically, the wobbling frequency componentcorresponding to the phase of the waveform at the inner circumferenceside border 14 of the groove track 270, for example, has a largeabsolute amplitude on the inner circumference side of the groove track,such as 270, and the absolute values of the outputs are greatest on theinner circumference side border 14 and smallest on the outercircumference side 15 of the groove track, such as 270. The wobblingfrequency component corresponding to the phase of the outercircumference side border of the groove track, such as 270, has a largeabsolute amplitude on the outer circumference side of the groove track,such as 270, and the absolute values of the outputs are greatest on theouter circumference side border 15 and smallest on the innercircumference side border 14 of the track, such as 270.

Therefore, when those absolute values are captured by the absolute valuedetectors 401, 402 of FIG. 20, the signals 524, 525 are detected as thebeam spot moves. When a difference between those signals is acquired bythe differential circuit 403, a track shift signal 526 without offsetcan be detected. By using this signal for tracking control, trackingcontrol can be performed with high accuracy.

Also, by using this signal, a track shift signal with offset can becorrected. The wobbling frequency component extracted from the signal521 by is removed by the differential circuit 407 to generate a trackshift signal which includes only an offset component. Thereafter, gainof the signal 526 is corrected by the gain correction circuit 404, andsignals are added by the adder 405 with their polarities matched, tothereby correct the offset component. As the offset correction method, awell-known method may be adopted. The track shift signal after thecorrection process has its track shift polarity switched according tothe polarity shift instruction of the land and groove tracks using thetracking polarity switching circuit 130, and sent to the trackingcontrol circuit 132.

As has been described, in the optical disk 4 according to each of theabove-mentioned embodiments, the inner and outer circumference sideborders 14, 15 of each track, such as 270 are wobbled with differentphases to record different items of address information 13 on the innerand outer circumference side borders 14, 15. Therefore, even if thediameter of the beam spot 1 during reproduction is larger than the trackwidth and the beam spot 1 extends over the tracks on both sides of thetrack from which data is to be read, the track can be identified byaddress information which has been read out. Accordingly, even if thetrack width is about one-half of the diameter of the beam spot 1, thetrack can be identified accurately to read information. Also inrecording, the track can be identified correctly to record informationmarks 274.

With the optical disk 4 in those embodiments of the present invention,even in the area where address information 13 has been recorded bywobbling of the borders 14, 15 of the track, such as 270, and theborders 14, 15 of the track 270, for example, have wobbling waveforms,user data or the like can be recorded by using information marks 274.For this reason, it it not necessary to provide areas dedicated torecording of address information 13 on the optical disk 4. Therefore,since it it not necessary to use, for example, the VFO unit for use whenreading address information 13, the user data recording efficiency canbe improved compared with the case of using address information recordedin the conventional preformatted header.

Furthermore, in the embodiment shown in FIG. 11, for example, a clocksignal can be generated from the wobbling waveform on the track, such as270, so that the sync area 12 is not required, thus making it possibleto improve the recording efficiency of user data.

Description will be made of the user data recording efficiency of theoptical disk 4 in this embodiment by comparing with the prior art. Inthis embodiment, address information 13 is recorded on borders on bothsides of a track, and therefore it is not necessary to secure on thetrack the areas for preformatting address information (ID) 259 as in theconventional ISO format in FIG. 25. Since the address information (ID)segment 259 is not required, those segments arranged to read the addressinformation segment 259, such as the VFO segment 257, the address marksegment 258, and the PA segment 263, become unnecessary. The sector mark(SM) segment 256 also becomes unnecessary because the same function isperformed by the sync area 12, SYNC segment, or the sync segment 1401 inthis embodiment. Further, in this embodiment, a reproducing clock signalcan be generated from the sync area 12 or the wobbling waveforms of thetrack, and therefore the VFO segment 252 and the RESYNC segment 268 inFIG. 25 become unnecessary. The clock generated from a signal from thesync area 12 may be used as a recording clock signal. Therefore, evenwhen a variation occurs in the rotating speed of the optical diskrotating motor, information marks can be recorded at a fixed frequency,so that the buffer 255 becomes unnecessary.

Accordingly, in the optical disk 4 in this embodiment, out of theconventional format in FIG. 25, 63 bytes of the preformatted header 250,69 bytes of the VFO segments 257, 252, 23 bytes of the buffer segment255, and 78 bytes of the RESYNC segment 268 become unnecessary. As aresult, the data recording efficiency of user data is 1014/1219 bytes,namely 84%. Note that in the conventional ISO format in FIG. 25, thedata recording efficiency of user data is 1024/1410, namely 72.6%.

In the third embodiment in FIG. 11, since a recording clock signal isgenerated from the wobbling waveform, the sync area 12 is not required,and thus the data recording efficiency can be further improved.

Therefore, according to the present invention, the user data recordingefficiency of the optical disk 4 can be increased to at least 80% sothat the data recording efficiency can be raised to an extremely highefficiency.

As is clear from the foregoing description, according to the presentinvention, there is provided an information recording medium with animproved track density, which has address information recorded inadvance so that information can be recorded or reproduced on a targettrack securely in recording or reproducing data. Also, an informationreproducing method and an information reproducing apparatus capable ofreproducing information from the information recording medium accordingto the present invention are provided. Moreover, a track forming methodand a track forming apparatus can be provided for forming a track on theinformation recording medium according to the present invention.

What is claimed is:
 1. An information recording medium consisting of atrack in which land sections and groove sections are alternately formed,wherein both said land sections and said groove sections are recordableareas in which information is recorded with information marks, bordersin a direction of said track of said land and groove sections arewobbled, and control information is recorded by said wobbled borders sothat information other than said control information, corresponding toat least 80% of said information which can be recorded in saidrecordable areas, can be recorded.
 2. The information recording mediumaccording to claim 1, wherein the period of wobbled waveforms of saidborders is fixed for each border, and the phases of the wobbledwaveforms of said borders are such that the waveforms of the opposingportions of adjacent borders facing each other across a respective trackare out of phase with each other by a predetermined phase difference. 3.An information medium consisting of a track in which land sections andgroove sections are alternately formed, wherein both said land sectionsand said groove sections are divided into a plurality of blocks and datais recorded in the blocks with information marks, borders in a directionof said track of said land and groove sections are wobbled, and controlinformation is recorded by said wobbled borders so that data other thansaid control information, corresponding to at least 80% of a capacity ofsaid blocks, can be recorded.
 4. The information recording mediumaccording to claim 3, wherein the period of wobbled waveforms of saidborders is fixed for each border, and the phases of the wobbledwaveforms of said borders are such that the waveforms of opposingportions of adjacent borders facing each other across a respective trackare out of phase with each other by a predetermined phase difference.